1. Field of Invention
The present invention relates to a ladder, and more particularly to a foldable ladder wherein all its step bars can be folded up laterally to form a compact structure for easy storage and carrying.
2. Description of Related Arts
Ladder has widely been used for several purposes, both domestic and industrial. It facilitates convenient and easy access to overhead working platforms which are frequently required for fixing and installing overhead equipments. A conventional foldable ladder comprises a front supporting frame and a back supporting frame pivotally connected with each other to form an inverted foldable xe2x80x98Vxe2x80x99 structure, wherein a plurality of unfoldable foot supporters is provided on the front supporting frame. The front frame and the back frame each comprises a first and a second side leg for supporting the ladder.
Conventionally, a so-called xe2x80x98foldablexe2x80x99 ladder is only foldable in the sense that its front frame can be pivotally folded toward the back frame or vice versa. In other words, it can only be folded in one-dimension. Very often, such one-dimensional folding still results in a bulky ladder which is inconvenient and difficult to store and carry. Due to huge demand of ladder, a more compactly folded ladder has been required and chased by consumers.
By a simple analysis of a conventional ladder, as described above, one may easily discover that if all the foot supporter could be folded to receive into two side legs of the ladder, the size of the ladder would be greatly reduced. But, from engineering""s point of view, folding all the foot supporters of the ladder while keeping its stability sound and supporting ability unaffected is somewhat difficult and baffling.
First and foremost, if the foot supporters are foldable, each of them is unavoidably movable. And if all the foot supporters are movable, their strength and stability of load carrying are difficult to ensure. Therefore, some sorts of highly reliable reinforcements have to be equipped to supplement the strength and stability lost and this is not successful for granted. If handled carelessly, the ladder will not be rigid enough and may cause harmful to its users.
Besides, in order that the foot supporters are foldable, each of which should be pivotally connected to the side leg in which it is mounted. Each foot supporter has a step surface formed between two ends thereof, when the ladder is in use, the step surface has to be horizontal so that the users are able to climb up along the ladder through the foot supporters. Typical pivotal joints only allow the foot supporters to pivotally move toward the side legs and no more. When the ladder is in use, the front and the back frame are usually fully unfolded and thus the side legs are inclined at an angle xcex8 with respect to the ground. If the foot supporters are mounted in such a manner that their respective step surfaces are horizontal when the front and the back supporting frames are folded, then, when the ladder is unfolded, the originally horizontal foot supporters will follow the unfolding motion of the side legs and finally, as in the case of the side legs, make an inclination with respect to horizontal.
Furthermore, every time the users fold and unfold the ladder, he, she has to fold or unfold each individual foot supporter. This not only brings huge trouble to the users, but also wastes the users"" time a lot.
A main object of the present invention is to provide a foldable ladder wherein when the ladder is fully unfolded, a step surface of each of the foot supporter is kept horizontal.
Another object of the present invention is to provide a foldable ladder which can be folded into a more compact size as compared with conventional foldable ladders for easy and convenient carrying and storage.
Another object of the present invention is to provide a foldable ladder comprising a plurality of foot supporters which can be folded up and received into the side legs of the ladder without sacrificing the supporting strength and stability of the ladder.
Another object of the present invention is to provide a foldable ladder wherein all the foot supporters can be folded up and unfolded simultaneously.
Another object of the present invention is to provide a foldable ladder wherein no expensive or complicated mechanical structure is employed to achieve the abovementioned objects.
Another object of the present invention is to provide a foldable ladder which can be easily operated and that no complicated folding and unfolding procedure is involved.
Accordingly, in order to accomplish the above objects, the present invention provides a foldable ladder which comprises:
a ladder supporting frame, comprising:
a back supporting frame which comprises a first and a second parallel back side legs; and
a front supporting frame which comprises a first and a second parallel front side legs each having an inner receiving surface formed thereon, wherein the first and the second front side legs are pivotally connected to the first and the second back side legs respectively so that the ladder supporting frame is capable of selectively folding between an operative mode and a standby mode, wherein in the operative mode, the front supporting frame is pivotally unfolded apart from the back supporting frame so that said front supporting frame is inclinedly supported with respect to horizontal, and wherein in the standby mode, the back and the front supporting frame are pivotally folded to overlap with each other;
means for retaining the ladder supporting frame in the operative mode;
a plurality of foot supporters, each comprising a first and a second step member, wherein each step member has an outer end portion, an inner end portion and a step surface formed therebetween;
a pivot joint pivotally connecting the inner end portions of the first and second step member;
a plurality of coupling arrangements spacedly supported by the first and the second front side legs respectively, wherein the outer end portions of the first and the second step member of each of the foot supporters are pivotally coupled with the coupling arrangements in such a manner that each of the foot supporters is capable of being folded between a folded position and an unfolded position, wherein in the folded position, the first and the second step member are pivotally folded toward each other so as to reduce a distance between the first and the second front side leg, wherein in the unfolded position, the first and the second step member are pivotally unfolded from each other to an extent that the step surfaces of the first step member is well-aligned with the step surface of the second step member; and
a foot supporter folding control mechanism, which comprises:
a folding controller pivotally connecting the pivot joints in such a manner that the folding controller is capable of folding the foot supporters simultaneously between the folded position and the unfolded position.